Coupling adapter base



FIG. 1 is a front perspective view of a coupling adapter base of the present design, which view also shows the bottom end and right side thereof;

FIG. 2 is another front perspective view thereof, which view also shows the top end and right side thereof;

FIG. 3 is a top end view thereof;

FIG. 4 is a front view thereof, the rear view being identical;

FIG. 5 is a right side view thereof, the left side view being identical;

FIG. 6 is a bottom end view thereof;

FIG. 7 is a perspective view thereof in a position of use; and,

FIG. 8 is a perspective view thereof in another position of use.

The broken lines are for the purpose of illustrating unclaimed portions and form no part of the claimed design. 

CLAIM The ornamental design for a coupling adapter base, as shown and described. 